The present invention relates to a sheet placement unit where the sheet bundle to which the folding process has been carried out is loaded, and the post-processing apparatus equipped with the sheet placement unit, the image forming system which includes the post-processing apparatus, and image forming apparatus, such as a copying machine and a printer.
Conventionally a post-processing apparatus carrying out the following processes is well known. The post-processing apparatus collects sheet-shaped papers (hereinafter referring to the sheet-shaped paper as only “sheet”), to each of which image forming has been carried out, into a bundle of plural sheets (hereinafter referring to as “sheet bundle”). After binding them, the post-processing apparatus performs a folding process and conveys the folded sheet bundle while the folding section is made into the leading edge, and accumulates the folded sheet bundles with a part of each of them overlapped with each other on a sheet ejection tray.
When a thick sheet or a sheet bundle which has been produced by folding multiple sheets is folded, the sheet tends to swell near the folding section and when loading this sheet bundle on a sheet ejection tray, it has had a problem that the pile of the sheet bundles is apt to collapse. Moreover, there has been also a problem that the leading edge of bundle of subsequent sheet enters the open folding section of precedent sheet, and a problem that the leading edge of the subsequent sheet bundle bumps into the trailing edge of the precedent sheet bundle, and pushes the precedent sheet bundle out from a sheet ejection tray.
The technique of equipping a stopper movable in the sheet conveying direction on a sheet ejection tray as a measure for these problems, and moving the stopper according to the increase of the sheet bundles conveyed into is disclosed (for example, refer to Unexamined Japanese Patent Application Publication No. 11-193162).
FIG. 9 is a figure showing the structure of a loading tray (sheet ejection tray) 32 disclosed in Unexamined Japanese Patent Application Publication No. 11-193162, and an operation of the loading stopper 37. FIG. 9a is a figure showing a state in which the loading quantity is small, and FIG. 9b is a figure showing a state in which the quantity is large.
The numerals 30 and 31 of FIG. 9 show the discharge rollers which discharge sheet bundle Pa, the numeral 35 shows a sheet holding arm and the numeral 35a shows the rotating shaft of the sheet holding arm 35, the numeral 35b shows the end of the sheet holding arm 35, and the numeral 35c shows a projection. Further, the numeral 45 shows the sheet height detection sensor which detects the height of the sheet holding arm 35. Inching of the loading stopper 37 is carried out in the sheet conveying direction A by a driving motor which is not illustrated so that sheet bundle Pa may be loaded smoothly, whenever new sheet bundle Pa is discharged.
However, in the technique disclosed by Unexamined Japanese Patent Application Publication No. 11-193162, a structure which makes the loading stopper 37 movable and a structure which makes the loading stopper 37 return to the initial location after termination of a series of the post-processing are required. Accordingly as a mechanism to return the loading stopper 37 or a driving motor capable of forward/reverse rotation is needed, it is easy to cause a higher cost. Moreover, generally, the sheet ejection tray of the post-processing apparatus which has a folding process and a binding process is installed at a lower portion of the post-processing apparatus in many cases, and when a sheet ejection tray extends horizontally, it needs to bend at the waist to take the sheet bundle, and it is a problem of not having enough workability.
On the other hand, the structure in which the sheet ejection tray is not level and is inclined in the direction so that the downstream-side of the sheet conveying direction becomes higher is also disclosed (for example, refer to Unexamined Japanese Patent Application Publication No. 2008-184311).
FIG. 10 is a figure for describing an operation for folded sheet bundles (paper sheet bundles) Pa1, Pa2, and Pa3 in the inclined folded bundle tray (sheet ejection tray) 840 disclosed by Unexamined Japanese Patent Application Publication No. 2008-184311.
In FIG. 10, the numerals 802, 803, 804 and 805 represent a flapper, a storage guide, a slippage roller, and sheet positioning member respectively. The numerals 813, 820, 840 and 842 represent a sheet bundle conveyance guide, a stapler, a sheet ejection tray and the 2nd loading surface respectively. The numerals 844 and 845 represent conveyer belts. Moreover, the numerals 849 and 860 represent a bundle detection sensor and a press unit (the 2nd folding device) respectively, and Pa1, Pa2, and Pa3 represent sheet bundles.
FIG. 10 shows the state where sheet bundle Pa1 is returned in the opposite direction (right) to the sheet conveying direction after the 2nd folding process of subsequent sheet bundle Pb2 by the press unit 860, after sheet bundle Pa1 is discharged on the sheet ejection tray 840 and it is conveyed leftward in the figure by the rotation of conveyor belts 844 and 845. By returning sheet bundle Pa1 in the opposite direction (right) of the sheet conveying direction, the lap of sheet bundle Pa1 over subsequent sheet bundle Pa2 is ensured.
In the technique which is disclosed by Unexamined Japanese Patent Application Publication No. 2008-184311, since it is easy to produce a swell near the folding section when using a thick sheet or a sheet bundle which is produced by folding multiple sheets, and as the sheet ejection tray 840 inclines, there is a possibility of remaining the problem that the lap of sheet bundles collapses easily. Moreover, because a forward/reverse rotation of the conveyor belts 844 and 845 is carried out while plural sheet bundles are loaded, there is a problem that the loaded sheet bundle collapses more easily. Further, like Unexamined Japanese Patent Application Publication No. 11-193162, since a driving motor which is capable of forward/reverse rotation is needed, it results in higher cost. Furthermore, it is worried that the leading edge of a consecutive sheet bundle enters the open part of the trailing edge of the sheet bundle which has been folded.
An aspect of the present invention is as follows.
1. A sheet placement unit on which a plurality of sheet bundles are loaded so that the plurality of sheet bundles are overlapped, with each sheet bundle of the plurality of sheet bundles having been produced by providing a folding process to a plurality of sheets and the sheet placement unit including a sheet placement section on which the sheet bundle having been provided with the folding process is loaded, and which is inclined so that a downstream side of the sheet placement section in the sheet conveying direction is higher than another side, a sheet conveyance device to convey the sheet bundle loaded on the sheet placement section in the sheet conveying direction while the plurality of sheet bundles are overlapped, and a sheet holding device provided swingably above the sheet placement section and including a sheet contacting section which comes in contact with an upper surface of the sheet bundle loaded on the sheet placement section.
2. A post-processing apparatus including a folding device for providing a folding process to the sheet bundle including a plurality of sheets, and the sheet placement unit of the abovementioned item 1.
3. An image forming system including the post-processing apparatus of the abovementioned item 2, a first control device which makes the sheet conveyance device convey the sheet bundle having been loaded on the sheet placement section in the sheet conveying direction when a sheet bundle having been provided with the folding process and being conveyed is placed on the sheet bundle having been loaded, and which stops the sheet conveyance device by detecting that a trailing edge of the sheet bundle having been provided with the folding process and being conveyed has arrived at the predetermined standby position by the sheet position detecting device, and an image forming apparatus including a plurality of mechanism sections for forming an image on a sheet, and a second control device which controls an operation of the plurality of mechanism sections and which is capable of communication with the first control device.